1. Field of the Invention
The present invention relates to an air amount computing unit and a fuel control unit of an internal combustion engine for vehicles such as automobiles and more specifically to the air amount computing unit for computing an air amount flowing into the cylinder of an internal combustion engine and to the fuel control unit for controlling a fuel injection amount by using the air amount flowing into the cylinder.
2. Background Art
As an engine control unit that calculates intake pipe pressure and a cylinder flow-in air amount on the basis of a throttle passing air amount, there is one that calculates the throttle passing air amount from an output of a throttle opening sensor, compares its temporal variation with a temporal variation of an intake air amount that is an output of an intake air amount sensor and corrects the throttle passing air amount inputted to the calculations of the cylinder flow-in air amount and of the intake pipe pressure on the basis of the comparison result to compensate a control delay as disclosed in JP Published Patent Application (Kokai) H9-158762 (1997) for example.
According to this engine control unit, when the engine is in a transient state, a filtering system that has the intake manifold pressure as an internal state variable is arranged to input a value in which a temporal variation of the intake air amount calculated based on the throttle opening is added to the intake air amount detected by the intake air amount sensor.
The calculation of the cylinder flow-in air amount in the prior art engine control unit is carried out by adding the temporal variation of the intake air amount calculated from the throttle opening angle to the intake air amount of only the input to the filter detected by the sensor and the intake air amount calculated from the throttle opening angle is not related to a previous filter output value inputted to the filter, so that an inflection point may occur in the next output and a desired air-fuel ratio may not be obtained as a result.
The present invention has been made in view of the problems to be solved and its purpose is to provide an air amount computing unit, and a fuel control unit, of an internal combustion engine that calculates the cylinder flow-in air amount during a transient state without a response delay and so as not to have any inflection point in changes of flow rate and that allows a desirable air-fuel ratio to be kept.